Prithviraj was born in Thiruvananthapuram, Kerala, to actors Sukumaran and Mallika Sukumaran. His elder brother Indrajith Sukumaran and sister-in-law Poornima Indrajith are also film actors. His initial schooling was at St. Mary's School Poojappura, which was near his home at Chengallur, where he acted in various plays and skits for the school's annual day celebrations. He completed the rest of his school education at the Sainik School Kazhakoottam, Thiruvananthapuram and Bharathiya Vidya Bhavan, Thiruvananthapuram. Prithviraj, along with his brother Indrajith, participated in debates and elocution competitions while in school. At the annual inter-school arts festival hosted by Loyola School, Thiruvananthapuram, Prithviraj won the title of "Mr LA Fest" twice, and is the only person to date to win that title twice. While pursuing his Bachelors in Information Technology at the University of Tasmania, Australia, he was called by film director Ranjith to play the lead role in his film Nandanam. It was Fazil, a well known Malayalam film director, who introduced him to Ranjith. After his performance in Nandanam, he decided to take a break from studies to concentrate on his film career. On 25th April 2011, Prithviraj married Supriya Menon, a BBC India Reporter.
In 2002, Prithviraj was cast by Ranjith in his second directorial venture, Nandanam. After this he appeared in films directed by Lohithadas, Vinayan, Kamal and Bhadran. He later went on to do Stop Violence and Swapnakoodu. Shyamaprasad, who cast him in lead role in his film Akale, said that Prithviraj's advantages are his talent and intelligence irrespective of his box office successes. In 2006, he played the role of Sub Inspector Solomon Joseph in the critically acclaimed Vargam. After Vargam, Prithviraj acted in Vaasthavam with the same director, M. Padmakumar, for which he received the Kerala State Award for Best Actor for 2006, and became the youngest actor to win the award. The same year he starred in Lal Jose's Classmates, which went on to become an all-time blockbuster, increasing his market value and giving Malayalam producers confidence to make more youth-oriented movies.
In 2007, he starred in Chocolate, directed by Shafi which was a huge success. In 2008, he starred in Thalappavu and Thirakkatha, in which he took up roles which serve as pivotal characters. One of the reviews of Thalappavu describes it as a film which is truly the coming-of-age film for Prithviraj the actor and that there is a Spartan dignity that he brings into his commanding portrayal of Naxalite Joseph. In 2009, the success of Prithviraj's Puthiya Mukham led the print and visual media to anoint him as "Superstar". His other releases in 2009 were Robinhood and Malayalam's first anthology film, Kerala Cafe. In 2011, Prithviraj turned producer through the multilingual film Urumi with him production company 'August Cinema'. The film had a good run in Kerala and was released in Telugu, Tamil, Hindi and English as well.
Prithviraj made his Tamil debut through Kana Kandaen in 2005 as the suave and sophisticated villain. Soon he got the opportunity to act under the direction of Bhagyaraj in the film Parijatham. Bhagyaraj said in an interview, "The entire media unanimously appreciated Prithviraj in Kana Kandaen, so it was with that confidence that I signed him". In 2007, Prithviraj co-starred with Tamil actress Jyothika Saravanan in her last film, Mozhi which went on to become a huge hit. He also starred in Satham Podathey and Kannamoochi Yenada in the same year. In 2008, Prithviraj starred in Vellithirai, the Tamil remake of Udayananu Tharam.
Prithviraj debuted in Telugu through Police Police in 2010. The film co-starred Srikanth, Kamalini Mukherjee and Sanjana. The film has been dubbed in Tamil as Kutrappirivu. Prithviraj has had many of his Malayalam films dubbed into Telugu like Sivapuram in 2006 which was the dubbing of Ananthabhadram and ATM in 2010 which was the dubbing of Robinhood. The dubbed version of his magnum opus film Urumi released in August 2011 to good response.